Temporary power

[SUNRAY]

Saturday morning I encountered a 32A/100mA 4 pole 3 phase EDIT non maintained active RCBO.

Not seen one before. It is installed as part of a portable generator inlet to a building. Builders hired the single phase genset and connecting cable to do some building work where the mains feed required isolating/moving and DNO attending.


Symptom... flip the lever over and push the green button, red marker in window goes black and buildings lights come on. Release green button and it trips/doesn't hold and building goes dark.


Hire company called out and declared their kit correct.

At this point I had given the reason but I'll leave it for a day or so for some thoughts/suggestions.

 

[jelliottelectrical]

Does the issue have to do with it being a single phase generator and the socket being 3 phase?

If so, have all the phases been connected to one phase via some sort of lead? Or some other shenanigans going on?
Failing that are they only trying to power up one phase?

My guesses would be that the RCD needs 415v to energise the ‘relay’ part of the RCD to keep it energised which isn’t happening as it’s a single phase generator

 

[EFLImpudence]

Symptom... flip the lever over and push the green button, red marker in window goes black and buildings lights come on. Release green button and it trips/doesn't hold and building goes dark.

I don't really understand that - or am I missing something really obvious?

How did you discover that you had to "flip the lever over" and "push the green button" to make the lights come on?


What is the "green button"? The test button or something else?

What does "flip the lever over" mean? Switch it on?

 

[jelliottelectrical]

It took me while but I presumed he meant turned the switch on and held in the test button (unless as it’s an active RCD this one has a ‘start’ button like a motor starter)

I basically took it as the RCD only stayed in while it was manually made to stay in

Something like this?

 

[SUNRAY]

The device made by Fanex occupies 5 units in an enclosure. (I'm annoyed I didn't take pics as there was a bit of a panic to get running and a web search doesn't find it) It has a 'rotary' lever very much akin to the original RCD's and marked '0' & '1', this gives a basic idea but looks nought like it:

and grey 'test' & green 'set' buttons.

Written instructions (magnifying glass required) say to switch on (it toggles with a clunk and power gets through) and hold then press green button. When both have been done the window goes black (it also works to press green then switch on and actually feels more positive that way). Green button mechanically holds lever on but releasing green button releases the lever.

It took me while but I presumed he meant turned the switch on and held in the test button (unless as it’s an active RCD this one has a ‘start’ button like a motor starter)

I basically took it as the RCD only stayed in while it was manually made to stay in

Yes correct, And thanks for the 'active' kick and I should have called it maintained (will edit to active)

Something like this?

I don't know the Chint unit but other similar devices I've encountered are basically an OCPD plus passive RCD bolted together.
This device is interlocked.

 

[jelliottelectrical]

Makes sense. So does the three phase rcd/single phase generator have any bearing on it?

 

[bernardgreen]

Did the 4 pole device trip / not reset if it detected significant un-balance on the 3 phases it was monitoring ?

If that is the case then with load only on one phase the device would determine the load ( 3 phase ) to be un-acceptably out of balance

 

[ericmark]

The old idea of the active RCD/RCBO is it will trip before the voltage drops to a level where the electronics will not work, and I have seen it with generators where some under voltage cut out is required. I have also seen where the AVR only monitors one phase, so loading up the wrong phase can cause under voltage, but your the guy with the volt meter.

 

[EFLImpudence]

Is the device similar to active RCD sockets and requires an earth connection to work?

 

[SUNRAY]

Makes sense. So does the three phase rcd/single phase generator have any bearing on it?

Well yes you are the closest.

It is a 3 phase inlet but only one phase required for lighting and power in the area the builders were working in, happened to be phase 2, so gen hire company made a cable 32/1 to 32/3 just neutral and ph2... simples, of course earth too.

Being an active RCBO device it required power to operate the internal solenoid and happened to use phases 1&2 as its source, with only phase 2 and neutral connected there was no path to power the RCBO workings.

 

[SUNRAY]

FWIW, DNO isolated the power to the meter and removed the 100A 3ph head, installed a new 200A feed from the sub approx 20m into a pillar, new head, meter, isolator. From there 70mm² tails into a new DB as planned/negotiated with builder. Seems to be a real bargain at £3.5K for bank holiday weekend.

Builder did all the digging, installed base & pillar, ducts & DB etc. I was surprised at how far DNO went.